1. Field of the Invention
The invention relates to workpiece supporting apparatus for use in conjunction with power tools, such as circular saws, having high speed cutting members. More precisely, the invention relates to apparatus for supporting irregularly edged or surfaced workpieces in a predetermined relationship to the high speed cutting member. p 2. Brief Description of the Prior Art
In woodworking, precision cutting such as sawing, notching, dadoing, etc., of a workpiece is often necessary. However, difficulty is encountered for such operations if the precision cutting must be done on a workpiece which does not have a flat surface or edge positionable adjacent an adjustable guide fence. Additionally, a workpiece surface which is available for cooperation with a guide fence may be quite irregular and may provide inadequate or unstable support.
For example, many common types of wood, especially soft boards of pine, fir or spruce, may become severely warped by changes in temperature, humidity, or merely by uneven pressures resulting from the manner in which the boards are stored. In order to avoid wasting of such warped and otherwise irregular boards it is frequently necessary to rip them to provide boards which have precisely cut parallel opposite edges.
To accomplish this end, various techniques have been used to rip such warped and irregular boards. One technique has simply been to guide an irregular edge of the warped board along the fence of a table saw. Accomplishment of such ripping is made more difficult by the fence member of certain table saws in that many such fence members are securely mounted at only one end. Such fence members may temporarily spring out of shape due to forces impressed against them during ripping of a badly warped board. During ripping, the warped board may cause "binding" of the high speed cutting edge of a saw blade, causing the wood to become hot and smoke. Frequently the cutting edge of the saw blade is heated to such a high temperature that the saw blade metal looses its temper and the cutting edge quickly becomes dull. The saw blade is useless once it has lost its temper, since it can not then be satisfactorily resharpened. Worse yet, the saw blade may grasp or "dig" into the warped board and propel it with sufficient force to endanger the workman.
Another technique has been that of employing a joiner to precisely straighten one edge of the irregular board; subsequently, a circular saw and a fence member thereof to guide the straightened edge may then be used to rip the irregular board to a predetermined width. However, a suitable joiner is an expensive tool and may not be available. Moreover, the process of making multiple passes of the irregular edge of the irregular board on a joiner may be a very time-consuming procedure and not justified in certain circumstances. Another possible solution to the problem is that of temporarily attaching (by clamping or nailing) a straight edge to the irregular board and pressing the temporary straight edge against the fence member of the power tool to guide the irregular board as it is moved past the cutting member. Again, this is an inconvenient and unwieldy procedure and has the detrimental effect of leaving permanent marks on the workpiece.
Various mechanisms have been utilized to secure a workpiece as it is moved past a rotary saw, as described and illustrated in U.S. Pat. Nos. 3,457,972 and 2,918,953. Various known fences and other equipment for use in conjunction with rotary saws and keyed with one or more grooves in the surface member of the rotary saw are known, but, such devices are very unwieldy and are unsuited to solving the problems discussed above.